This invention relates to an exhaust manifold for conducting exhaust gases from an engine block toward exhaust piping. In particular, this invention relates to an exhaust manifold having baffles arranged in a common space within the manifold to divide the space into a plurality of passageways thereby controlling the flow of exhaust gas through the manifold for engine performance tuning. More particularly, this invention relates to a tuned exhaust manifold of sheet metal construction having drop-in baffles.
Engine performance tuning is typically accomplished by means of an exhaust "header" type system. A conventional exhaust header comprises a plurality of individual elongated tubes for coupling each of the cylinder heads of an engine block to a remote manifold chamber or exhaust pipe. Adjacent exhaust ports in the engine block are "isolated" by the separate header tubes in order to tune engine performance. It is impractical to install header systems in many vehicles since these systems generally take up a significant amount of the small available space in the engine compartment. In addition, these header systems often require costly and complex welds and bends. See, for example, U.S. Pat. No. 4,373,331 to Santiago et al.
Conventional exhaust manifolds usually comprise heavy cast metal tanks coupled directly to the engine block in a position to receive engine exhaust gases. See, for example, U.S. Pat. No. 4,301,775 to Smart et al. The added weight provided by cast metal manifolds is known to affect fuel efficiency and hamper engine performance.
It is known to form an exhaust manifold using stamped sheet metal members. U.S. Pat. No. 4,537,027 to Harwood et al. discloses only an exhaust manifold of conventional configuration which has a housing formed of sheet metal construction.
U.S. Pat. No. 3,940,927 to Maurhoff et al. discloses a sheet metal shell containing a freely movable reactor chamber for afterburning engine exhaust gasses. The reacter chamber is freely movable within the shell in accordance with the thermal distortions of the reactor to minimize resulting stresses in the reactor. Maurhoff et al. does not address the problem of "tuning" an exhaust manifold.
U.S. Pat. No. 4,373,331 to Santiago et al. discloses a tubular manifold including two half-stampings welded together to form a plurality of separate exhaust tubes. A considerable amount of welding is necessary to join these two half-stampings together due to the tubular configuration of the Santiago et al. manifold. Also, the continuous webs interconnecting the exhaust tubes disclosed in Santiago et al. add additional weight to the manifold assembly. Although such a tubular design does permit "tuning" of the various runners, it does not provide the compactness required for many crowded underhood conditions.
One object of the present invention is to provide an exhaust manifold which eliminates complex welding and bending of tubes yet is configured to permit engine performance tuning.
Another object of the present invention is to provide a compact tuned exhaust manifold which is light weight, rigid, and easy to manufacture.
Yet another object of the present invention is to provide a stamped split exhaust manifold housing with drop-in baffles to divide a common space in the housing into a plurality of separate exhaust gas passageways configured to performance-tune the exhaust manifold.
Still another object of the present invention is to provide a method of assembling a tuned exhaust manifold which is simple and requires a minimum number of welded joints.
In accordance with the present invention, an improved exhaust manifold is provided for attachment to an engine having a plurality of exhaust ports and is configured to permit performance tuning of the engine. The manifold includes a housing formed to include an exhaust chamber and baffle means in the exhaust chamber for partitioning the exhaust chamber into a plurality of separate passageways to performance-tune the exhaust manifold.
The housing is formed to include inlet means for admitting combustion product discharged from the engine exhaust ports into the exhaust chamber and outlet means for exhausting combustion product from the exhaust chamber. The baffle means is fixed in a predetermined position to define separate passageways connecting each of the engine exhaust ports to the outlet means. The baffle means acts to isolate the flow of combustion product discharged into the exhaust chamber from each engine exhaust port substantially into a companion passageway as it is conducted through the housing.
In preferred embodiments of the present invention, the housing includes a stamp-formed sheet metal inner shell providing the inlet means and a stamp-formed sheet metal outer shell attached to the inner shell at a perimetrically-extending split line. The inner and outer shells cooperate to define a flange-receiving space therebetween at the split line which opens into the interior of the housing. In addition, the inner and outer shells are each configured to define interior regions which cooperate to provide the exhaust chamber when the inner and outer shells are joined together. At least one of the inner and outer shells can include dimple means for aligning the baffle means in a predetermined pattern within the housing during assembly of the exhaust manifold.
The baffle means includes a plurality of stamped sheet metal tuning baffles situated in predetermined positions within the exhaust manifold. The baffles are arranged to divide the exhaust chamber into a plurality of separate combustion product-conducting passageways. Each passageway distributes combustion product from one of the inlet openings formed in the inner shell to the outlet means and effectively isolates individual engine exhaust ports for engine performance tuning.
Each tuning baffle includes a flange means and an integral tongue portion. The flange means is inserted into the flange-receiving space to attach the baffle to the exhaust manifold at the split line. In that manner, each baffle is dropped into the housing and retained at its predetermined position within the exhaust chamber. The tongue section is canted at a predetermined angle relative to the flange means. The tongue section of a mounted baffle extends into the interior region of the inner shell so that a distal end of the tongue section is positioned in close proximity to a selected inlet opening in the inner shell. The shape of the tuning baffles and the predetermined angles between the tongue sections and the flange means are selected in accordance with a predetermined specification to performance-tune the engine.
Also in accordance with the present invention, an improved method is provided of assembling a split-housing exhaust manifold having a plurality of tuning baffles disposed therein. Illustratively, the method includes the steps of providing an inner shell formed to include a plurality of inlet openings for communicating with exhaust ports of an engine and a perimetrical lip defining an opening, placing a portion of each tuning baffle on the perimetrical lip, positioning each tuning baffle in a predetermined location, inserting an outer shell into the opening defined by the perimetrical lip of the inner shell, and bonding the outer shell to the inner shell at a split line between the inner and outer shells to secure each tuning baffle rigidly in its predetermined position. Using this novel technique, each tuning baffle is positioned in a predetermined location in a common space in the exhaust manifold to isolate each exhaust port of the engine in its own passageway within the manifold so that the engine is performance-tuned.
In preferred embodiments of the present invention, the inner shell includes an interior wall having a plurality of groups of inwardly-extending dimples. Preferably, the method further comprises the step of moving each tuning baffle on the perimetrical lip to engage a selected group of inwardly-extending dimples. Thus, the dimples operate to provide means for aligning the baffles in the predetermined positions within the exhaust chamber during assembly of the exhaust manifold.
One feature of the present invention is the provision of tuning baffles in the interior of a compact exhaust manifold suitable for direct attachment to an engine block or head. This feature advantageously conserves underhood space in marked contrast to known exhaust headers or other tuned exhaust manifolds. The tuning baffles act to divide the interior of the exhaust manifold into a plurality of separate passageways. Such division of a common space in the manifold effectively isolates the incoming flow of combustion product discharged into the manifold by each engine exhaust port. Such flow isolation advantageously reduces intermixing in the exhaust manifold of combustion product discharged by the individual exhaust ports in the engine block or head and controls the back pressure at each inlet opening in the inner shell and the corresponding engine exhaust port.
Another feature of the present invention is the provision of tuning baffles having flange means for mounting in an inwardly-opening perimetrical space defined by the inner and outer shells at the split line of the housing. In the tuned exhaust manifold of the present invention, the inner and outer shells which cooperate to provide the manifold housing are configured to form the split line and the inwardly-opening, flange-receiving space at a location approximately midway between the manifold inlet mounting flanges and the portion of the mounted exhaust manifold that is the greatest distance away from the engine block. This novel split-line location permits tuning baffles of a wide variety of shapes, contours, and sizes to be captured or trapped in the flange-receiving space in the housing to divide the interior exhaust chamber into the separate flow-isolating passageways. Thus, the improved exhaust manifold of the present invention can be tuned in accordance with virtually any design specification by varying the shape of the tuning baffles and the arrangement of the baffles within the exhaust chamber while always securing the baffles in a predetermined position via a rigid attachment to the housing at the split line.
Moreover, the foregoing features advantageously simplify the manufacturability of a tuned exhaust manifold by replacing the complex welds and pipe bends of conventional tubular tuned exhaust systems with the novel trapped baffle assembly of the present invention. Thus, the tuning baffles may be stamp-formed of sheet metal, thereby eliminating the need to perform complex, costly, and time-consuming welding procedures on conventional irregular, elongated pipe bends. These novel stamped tuning baffles are especially well-suited for use in combination with stamp-formed sheet metal housing shells when assembled using the novel method of the present invention.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art on consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.